The HERC5 Knockout SK-HEP-1 Polyclonal Cells are a CRISPR/Cas9-edited polyclonal knockout pool derived from the human SK-HEP-1 hepatic adenocarcinoma cell line, in which the HERC5 gene has been disrupted to create a loss-of-function model. This polyclonal population provides a heterogeneous mixture of edited cells, avoiding the clonal bias of monoclonal lines, suitable for studying HERC5-dependent processes. HERC5 encodes an interferon-induced E3 ISG15 ligase that catalyzes the conjugation of ISG15, a ubiquitin-like modifier, to target proteins, playing a critical role in antiviral innate immunity.
The SK-HEP-1 host cell line was established from a patient with liver adenocarcinoma and exhibits features of both endothelial and mesenchymal cells, often characterized as hepatic sinusoidal endothelial-like. As an adherent, tumor-derived line, SK-HEP-1 is a well-established model in hepatocellular carcinoma research and studies of liver sinusoidal cell biology. Its hepatic origin also makes it a relevant system for examining liver-tropic pathogens, particularly hepatitis C virus, and for probing interferon signaling in a hepatocellular context.
Mechanistically, HERC5 operates downstream of interferon signaling. Stimulation by type I (IFN-??/??) or type II (IFN-??) interferons initiates JAK-STAT pathway activation, where receptor-associated JAK1 and TYK2 phosphorylate STAT1 and STAT2, leading to the formation of ISGF3 complexes (STAT1-STAT2-IRF9) that transcriptionally induce HERC5 and ISG15. Additionally, upstream regulators IRF3, IRF7, and NF-??B contribute to HERC5 expression. Once produced, HERC5 acts as the E3 ligase in a three-enzyme ISGylation cascade, working with the E1 enzyme UBE1L and E2 enzyme UBE2L6 to covalently attach ISG15 to lysine residues on diverse substrates. Critical targets include IRF3, STAT1, the tumor suppressor p53, and filamin B. This post-translational modification regulates protein stability, subcellular localization, and function, thus coordinating antiviral responses and potentially linking ISGylation to cellular growth and apoptosis control.
In the SK-HEP-1 cell line, which retains interferon-responsive machinery alongside tumorigenic properties, knockout of HERC5 eliminates ISG15 conjugation, enabling precise dissection of ISGylation contributions to interferon signaling dynamics. Key substrates such as STAT1 and IRF3 are central to antiviral gene expression; thus, HERC5 disruption is expected to alter the magnitude or kinetics of these responses. Moreover, using this liver adenocarcinoma model, researchers can explore intersections between ISGylation, hepatocellular carcinogenesis, and viral hepatitis. Loss of HERC5-dependent ISGylation may reveal roles for ISG15 modification in tumor cell proliferation, migration, or immune evasion, offering insights relevant to both oncology and virology.
This polyclonal knockout cell population is well-suited for experiments aimed at clarifying HERC5 function and ISGylation biology. Standard assays include western blotting to detect ISG15 conjugates and assess global ISGylation, RT-qPCR for interferon-stimulated gene expression, and immunofluorescence microscopy for ISG15 localization. Functional studies may employ HCV replication assays to measure viral permissiveness or flow cytometry for phospho-STAT1 as a readout of JAK-STAT activation. The model supports research in antiviral innate immunity, ubiquitin-like modifications in liver cancer, and interferon signaling in hepatic cells. For further technical details, please contact Ascent Research.
